JP2534343B2 - Ultrasonic linear motor - Google Patents

Description

TECHNICAL FIELD The present invention relates to an ultrasonic linear motor suitable as a drive source for electronic devices and precision machines.

[Prior Art] In recent years, an ultrasonic motor using ultrasonic vibration of a piezoelectric element made of piezoelectric ceramics as a drive source has been developed and used as an actuator for various devices. Such an ultrasonic motor is expected to be small and have high torque.
The piezoelectric element is advantageous in that it does not generate electromagnetic waves and does not affect the electromagnetic medium.

In the ultrasonic motor, a vibrating driving body and a driven body are arranged close to each other, and vibration in the feeding direction of the driving body is transmitted to the driven body via friction. The driving body performs oblique linear vibration or elliptical vibration that is a combination of vibrations in directions orthogonal to each other, and if this is structurally classified,
There are three types, vibrating reed type, torsional oscillator type, and traveling wave type.

As shown in FIG. 18, the vibrator element type ultrasonic motor has a vertically vibrating piezoelectric vibrator 11 and a vibrator element 12 attached to the piezoelectric vibrator 11, which are installed obliquely with respect to a contact surface of a driven body 13. Driven body
It is driven by pushing 13 in a certain direction, and has high energy conversion efficiency and can operate at high speed.

Further, as shown in FIG. 19, the torsional vibrator type ultrasonic motor has a piezoelectric vibrator 14 provided with a torsional coupling element 15, and the longitudinal vibration of the piezoelectric transducer 14 causes the torsional coupling element 15 to bend and deform. By making a rotational displacement around the axis of the piezoelectric vibrator 14, the elliptical vibration is generated instead of the linear vibration like the vibrating bar type.

As shown in FIG. 20, the traveling wave type ultrasonic motor has a piezoelectric element 17 bonded to a vibrating body 16 formed in an annular shape or a disc shape, and a flexural vibrating wave traveling in the circumferential direction is applied to the vibrating body 16. By giving it, the contact surface with the rotor 18 is caused to oscillate in an elliptical manner, and there is an advantage that the wear is small because the contact area is large.

[Problems to be Solved by the Invention] However, in the conventional techniques as described above,
In each case, there were the following issues to be solved.

First, in a vibrating piece type ultrasonic motor, the vibrating piece 12
Since the contact between the driven body 13 and the driven body 13 is intermittent, the rotation is unstable, and the feeding direction of the driven body cannot be changed and is constant. Further, there is a problem that the tip of the rotor vibrating piece 12 is severely worn.

The torsional vibrator ultrasonic motor has drawbacks such as the need for a linear motion conversion mechanism when used as a linear motor.

The traveling wave type ultrasonic motor has a drawback that the energy conversion efficiency is low and a linear motion conversion mechanism is required as described above. Further, as a signal wave type ultrasonic linear motor, a linear vibrating body is installed instead of the ring-shaped or disc-shaped vibrating body 16, and a traveling wave is given to this to transmit the vibration to the driven body. However, in this case, since the traveling wave is excited in the entire rail, there is a drawback that the energy loss is further increased and the efficiency is reduced.

It is an object of the present invention to provide an ultrasonic linear motor which utilizes ultrasonic vibration and has a simple structure with good energy efficiency.

[Means for Solving the Problems] In order to solve the above problems, the present invention configures a vibrating body including a pair of legs and a body connecting the legs using an elastic body, A vibrating element is attached to the body obliquely with respect to the axis of the leg portion to vibrate the vibrating body. Although the shape of the vibrating body and the mounting method of the vibrating element are appropriately selected,
We have found that the structure in which a pair of vibration elements are attached near the end of the body has high energy efficiency. An efficient driving method was to set the phase difference of vibration between the vibrating elements to around 90 degrees. As the vibration element, a piezoelectric element using piezoelectric ceramics is usually used.

In the above ultrasonic linear motor, the angle formed by the vibrating element and the body portion is usually set to be equal to each other on the left and right sides, but to be a complementary angle. By doing so, the vibration can be divided and efficiently transmitted to the leg and the body, and a large elliptical vibration can be efficiently generated at the tip of the leg. Further, the angle formed by one vibrating element with respect to the body portion or the leg portion is not limited to 45 degrees, and may be appropriately determined in consideration of distribution of vibration component force.

[Operation] In the ultrasonic linear motor configured as described above, when the vibrating body is vibrated by the vibrating element, the body and legs are integrated as a unit including the vibrating element, and the material, size, shape, and vibration Standing wave vibration is generated according to the frequency.
This vibration causes vertical vibration that expands and contracts the body and leg in the lengthwise direction and bending vibration that deforms these members in the widthwise direction. As a result of these vibrations, an ellipse is formed at the tip of the leg. Excites vibration. Therefore, by bringing the tips of the legs into contact with another member (driven member), this member and the vibrating body can be moved relative to each other.

The elliptical vibrations at the tips of the two legs may be in the same phase, but if an appropriate phase shift is generated, the efficiency can be further improved. To this end, a pair of vibrating elements is provided on each leg. They are arranged, and the phase of the alternating power source is appropriately shifted.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

In FIGS. 1 and 2, 1 and 2 are leg portions parallel to each other, and 3 is a body portion that connects one ends of these leg portions 1 and 2. In these, the vibrating body 4 is configured by molding an elastic material in which each section has a substantially square cross section and is formed into a U shape as a whole. This dimension is designed as appropriate, but the example is made of aluminum with a body of 5 mm □ × 26 mmL and legs of 5 mm □ × 10 mmL. The vibrating body 4 is made of duralumin,
A metal material such as iron, brass or stainless steel, an inorganic material such as alumina, glass or silicon carbide, an organic material such as polyimide resin or nylon can be used.

The corners of the vibrating body 4 are chamfered to form an angle of 45 degrees with the legs 1 and 2 and the body 3, and the piezoelectric elements (vibrating elements) 6 and 7 are attached to the mounting surface 5. It is attached using an adhesive or the like. As the piezoelectric elements 6 and 7, a laminated piezoelectric actuator made of PZT (lead titanate zirconate) or a single-plate piezoelectric ceramic is used, and the piezoelectric elements 6 and 7 expand and contract in the direction orthogonal to the mounting surface 5. .
As the piezoelectric elements 6 and 7, those of 5 mm □ × 9 mmL are used.

The vibrating body 4 has leg portions on the upper surface of the rail (driven body) 8.
It is used by touching the lower ends of 1,2. On the upper surface of the rail 8, there is a groove 8a having a width for fitting the lower ends of the legs 1 and 2 in the longitudinal direction thereof.
Are formed.

Next, the mechanism of movement when vibration is applied to the ultrasonic linear motor will be described based mainly on the results of FEM analysis (computer analysis using the finite element method).

FIG. 3 is a prototype of the ultrasonic linear motor of the present application, which is composed of a vibrating body 4a having only legs and a piezoelectric element 6.

4 and 5 show the results of a simulation using the finite element method (FEM) when an AC voltage of V = E · sinωt is applied to the piezoelectric element 7 of the ultrasonic linear motor of FIG. Is. The vibration of the piezoelectric element 7 is transmitted to the vibrating body 4a via the mounting surface,
The component parallel to the axis of 4a gives a longitudinal vibration, and the component perpendicular to the axis gives a bending vibration, and as a result, an elliptical vibration is excited at the tip. Therefore, when the driven body 8 is pressed against the lower end surface of the vibrating body 4a with a constant pressure, the vibrating body 4a and the driven body 8 relatively move along the direction of the elliptical vibration. When the driven body is the rail 8 as shown in FIG. 3, the vibrating body 4a is used.
Will move. In this ultrasonic linear motor, since the mode of longitudinal vibration or flexural vibration differs depending on the frequency of the vibration source, the traveling direction can be changed by appropriately selecting this vibration frequency. The relationship between the frequency and the vibration mode and the resulting advancing direction, energy efficiency, driving torque, etc. are determined by the vibration characteristics of the structure in which the driving body 4a and the piezoelectric element 6 are integrated.

The ultrasonic linear motor of the present application has a structure in which the upper end of the vibrating body 4a is connected by the body portion 3 and basically uses the same principle, but is not simply considered the same. If only the legs are considered separately, it is considered that each independently makes an elliptical vibration as shown in FIG. 5, but the efficiency is even higher.

6 and 7 show that an AC voltage of Va = E · sinωt is applied to the first piezoelectric element 6 (on the left side in FIG. 1) and Vb = E · cosωt is applied to the second piezoelectric element 7. It shows a result of a simulation using a finite element method (FEM) when an AC voltage is applied.

The vibration of the piezoelectric element 7 is transmitted to the body 3 and the legs 1 and 2 of the vibrating body 4 via the mounting surface 5, and the component parallel to the axis is vertical vibration, and the component perpendicular to the axis is flexural vibration. give.
The elliptical vibration excited at the lower ends of the legs 1 and 2 is the result of combining all of the longitudinal vibration and flexural vibration of the body 3, and the longitudinal vibration and flexural vibration of the legs 1 and 2, and their vibration modes are As described above, the vibration characteristics of the structure in which the vibrating body 4 and the piezoelectric elements 6 and 7 are integrated, the frequency of the power supply applied to the piezoelectric elements 6 and 7, and the alternating power supply to the left and right piezoelectric elements 6 and 7. It is determined by the phase difference and the like. Factors that determine the vibration characteristics of the structure include
Examples of the material include the material (e.g., elastic modulus), shape (cross-sectional shape, ratio of the lengths of the body and legs), size, and pressure contact force between the vibrating body 4 and the driven body of the vibrating body 4.

Regarding the material of the vibrating member 2, the larger the elastic modulus is, the smaller the energy loss due to internal wear is, but the smaller the vibration displacement is. Therefore, the material having the most energy efficiency is selected comprehensively. Also, regarding the size and shape, the vibrating body 4 is used.
The larger the height, the smaller the cross section, and the flatter the cross section in the direction orthogonal to the traveling direction, the larger the amplitude of the flexural vibration.

Therefore, if the size, material and shape are set and the vibration frequency and the phase difference between the left and right piezoelectric elements 6 and 7 are properly selected, the longitudinal vibration and flexural vibration of the body 3 and the legs 1 and 2 can be effectively performed. As a result, elliptical vibration with large amplitude is caused at the lower ends of the legs 1 and 2. The elliptical vibrations of the left and right legs 1 and 2 are not necessarily the same shape. In the example shown in the figure, the sin wave side is relatively laterally flat as shown in FIG. As shown in Figure (b), the cos wave side is vertically flat.
In the illustrated example, the vibration source frequency is set to 91.181 kHz.

FIG. 9 and FIG. 10 show another embodiment of the present invention, in which a pair of front and rear wheels 11 having an axle 10 supported by a support frame 9 is provided on the lower portion of the rail 8. That is, the beam member 12 is fixed to the upper surface of the body portion 3.
Elastic members (coil springs) 13 are stretched between both end portions of the support frame 9 and the center of the support frame 9, and the coil springs 13 cause the lower surfaces of the legs 1 and 2 to be on the upper surfaces of the rails 8 and the wheels 11. Are pressed against the lower surface of the rail 8. This coil spring 13
Is selected to have an appropriate elastic coefficient according to the applied load. This example has the advantage that it can be used even when the rail is tilted or upright.

FIGS. 11 to 17 show another embodiment of the present invention in which the mounting positions of the piezoelectric elements 6 and 7 are changed.

FIG. 11 shows the piezoelectric elements 6 and 7 attached inside the corners of the vibrating body 4, FIG. 12 shows the outside of the corners protruding and attaching them to the tips, and FIG. 13 shows the inside of the corners protruding. Then, one is attached to the outside and the other is attached to the inside, as shown in FIG. Further, in FIG. 15, the position of the body 3 is slightly lower than the upper ends of the legs 1 and 2, and the piezoelectric elements 6 and 7
Axis of the body 3 intersects the axis of the body 3 at the end of the body 3, FIG. 16 shows that the positions of the legs 1 and 2 are slightly inside the end of the body 3, In the figure, the position of the trunk 3 is the leg
It is slightly lower than the upper ends of 1, 2 and the mounting surface 5 of the piezoelectric elements 6, 7 faces inward.

Since each of these has structural features,
It may be selected depending on the usage of the linear motor.
The relationship between the traveling direction and the phase difference is different from that described above, but the basic idea is the same.

In these examples, the angle formed by the body portion 3 and the piezoelectric elements 6 and 7 is 45 degrees, but the angle is not limited to this, and it is sufficient if the body portion 3 and the piezoelectric elements 6 and 7 form an equal angle or a complementary angle.

Further, the phase difference of the power supply voltage applied to both piezoelectric elements is 90 degrees in the above-mentioned embodiment, but since this value seems to be the most efficient, an appropriate value between 10 and 170 degrees is used. It may be a value.

In the traveling body 4 of the embodiment shown in FIG. 1, when a driving voltage of 5.0 V is applied to the longitudinal vibration element 3 between peaks, the driving voltage frequency is 105 kHz, and the pressure contact force is 1.0 kg · f, no load is applied. The maximum speed was 0.3 m / sec. Although the above-mentioned frequency is the most efficient, it was confirmed that it works practically in the range of 80 to 120 kHz.

In the above example, a piezoelectric element made of PZT was used as the vibration element, but other vibration elements,
For example, a magnetostrictive element or the like may be used.

[Effects of the Invention] As described in detail above, the present invention constitutes a vibrating body composed of a pair of leg portions and a body portion connecting the leg portions using an elastic body as a material, and the vibrating body is provided with an axis line of the leg portions. Since a vibrating element that is obliquely attached to vibrate the vibrating body is attached, longitudinal vibration and flexural vibration are caused in the body and leg, respectively, and as a result, an ellipse with large amplitude is formed at the tip of the body. Vibration can be excited. Therefore, by applying standing wave vibration to the vibrating body and converting it to linear motion,
It is possible to provide an ultrasonic linear motor with good energy efficiency. In addition, a pair of vibrating elements are arranged near the end of the body and a phase difference is applied to these alternating power sources to enhance longitudinal vibration and flexural vibration and further improve energy efficiency. By mounting it diagonally with respect to the axis of, it is possible to efficiently transmit the vibration by dividing it into the body and leg, and the vibration transmitted by dividing this can generate a large elliptical vibration at the tip of the leg. It is possible to provide an ultrasonic linear motor having a high energy transmission efficiency with a simple configuration in which the vibrating body is obliquely attached to the axis of the leg.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention, FIG. 2 is a side view thereof, FIG. 3 is a perspective view of an ultrasonic linear motor to show its principle, and FIGS. The figure which shows the FEM analysis result of the ultrasonic linear motor of the figure, FIG. 6 thru | or 8
FIG. 9 is a diagram showing the result of FEM analysis of the ultrasonic linear motor of the present invention, FIG. 9 is a side view showing another embodiment of the present invention,
FIG. 10 is a front view thereof, FIGS. 11 to 17 are side views showing still another embodiment, and FIGS. 18 to 20 are sectional views showing a conventional example. 1,2 ... Legs, 3 ... Body, 4 ... Vibrator, 6,7 ... Vibration element (piezoelectric element).

Claims (3)

(57) [Claims] 1. A vibrating body comprising a pair of leg portions and a body portion connecting the leg portions made of an elastic body, the vibrating body being obliquely attached to the vibrating body with respect to an axis of the leg portion. An ultrasonic linear motor characterized in that a vibrating element for vibrating is attached. 2. The ultrasonic linear motor according to claim 1, wherein the vibrating elements are attached one by one near the end of the body. 3. A vibrating element, which is made of an elastic material and is composed of at least a pair of legs, is provided with a vibrating element positioned obliquely with respect to the axis of the vibrating element to vibrate the vibrating element. An ultrasonic linear motor, characterized in that longitudinal vibration and flexural vibration can be excited at one end of the leg portion by one.